libmailutils6 1:3.6-1build1 (amd64 binary) in ubuntu focal

 GNU Mailutils is a rich and powerful protocol-independent mail framework.
 It contains a series of useful mail libraries, clients, and servers.
 .
 This is GNU's Mail abstraction library. This library allows programs to
 hook into a single library for many different types of mail backends.
 The following backend stores are currently provided: mbox, mh, maildir,
 pop3, imap4.